Jimmy Dean, there are some good and bad products out there for this. Stay away from the cheap plastic set ups. I know the member "sharkracing" has musical horns on his 2005 Newell and on his Freightliner Sportchassis and a lot of people I'm told get a kick out of it. It can go really loud and clear. Hopefully he will chime in and tell us what brand he installed and maybe the ones to stay away from.

This project is the result of someone cutting in front of one of their family members while cruising at speed. This guy decided a set of Nathan Train horns would work better next time versus his OE RV horns...
Fully automated, these horns are on a custom slide system that push the horns out after the fiberglass nose is pushed out and up on their own slide system.

The company I and a few other racers have purchased and installed are from Horn Blasters. They kick butt period. Awesome quality not cheap plastic. You can buy a complete new kit with an air supply or without.